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Home My WebLink AboutSubsoil Studyl(+ltårffi¡fi'tr*"¡:Ë:f*'l:3ü**' An Employco Owncd Compony 5020 County Road 154 Glenr¡'ood Splings. CO 8ló01 phone: (970) 945-7988 1àx: (970) 945-8454 emai I : kaglenu'ood@kumalusa.corrr wu'rt'.kunlalusa.con.l Ofl'ice Loc;ations: I)envs (l lQ)" Parker. Colot'atlo Springs. Fort flollins, Cleurvood Springs. atld Sumnlit Count-r', Colorado June 7,2021 Caleb Koski P.O. Box 4185 Basalt, Colorado 81621 bi rds. beware@,lrotnrai l.corn Project No.2l -7-392 Subject: Subsoil Study for Foundation and Septic Design, Proposed Residence, 893 County Road 102, Missouri Heights, Garfìeld County, Colorado Dear Caleb: As requested, Kumar & Associates, Inc. performed a subsoil study for foundation design and septic disposal feasibility at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to you dated April 30,2021. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed residence will be a72' by 40' shop withmezzantne residence located on the site in the area of the pits shown on Figure l. Ground floor will be slab- on-grade. Cut depths are expected to range between abou't 2 to 4 feet. Foundation loadings for this type of construction are assumed to be relatively light to moderate and typicalof the proposed type of construction. The septic disposal system is proposed to be located west- northwest of the building area. If building conditions or foundation loadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The site is open pasture land, gently sloping down to the west. Site grading appears natural and vegetation consists of grass and weeds with sage and rabbit brush. There is an existing house on the property located several hundred feet to the south ofthe proposed building area. Subsidence Potential: The site is underlain by Pennsylvania Age Eagle Valley Evaporite bedrock. The evaporite contains gypsum deposits. Dissolution of the gypsum under certain 1 conditions can cause sinkholes to develop and can produce areas oflocalized subsidence. Widely spaced sinkholes have been observed in the Missouri heights area. Sinkholes were not observed in the immediate area of the subject lot. The pits dug on the site were relatively shallow, for foundation design only. Based on our present knowledge of the site, it cannot be said for certain that sinkholes will not develop. In our opinion, the risk of ground subsidence at this site is low and similar to other sites in the area but the owner should be aware of the potential for sinkhole development. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits in the building area and two profile pits in the septic disposal area at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about one foot oftopsoil, consist of2Yzto 3/z feet ofstiff, sandy silty clay overlying stiff, whitish sandy silt down to the pit depths of 6 to 9 feet. Results of swell-consolidation testing performed on relatively undisturbed samples of the sandy silty clay and sandy silt, presented on Figures 3 and 4, indicate low compressibility under existing moistúre conditions and light loading and a minor to low collapse potential (settlement under constant load) when wetted. Results of USDA gradation analyses performed on samples of the upper loam and deeper silt loam obtained from the site are presented on Figures 5 and 6. The laboratory test results are summarized in Table l. No free water was observed in the pits at the time of excavation and the soils were slightly moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 2,000 psf for support of the proposed shop/residence. The soils tend to compress after wetting and there could be post-construction foundation settlement mainly depending on the depth and extent of wetting. Footings should be a minimum width of l8 inches for continuous walls and 2 feet for columns. Loose and disturbed soils encountered at the foundation beáring level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. We should observe the completed foundation excavation to confirm suitable bearing conditions. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be heavily Kumar & Associates, lnc. @ Project No. 21'7-392 J reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures (if any) should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for the on-site soil as backfill, excluding organics and rock larger than 6 inches. Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab controljoints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of 3/+ inch road base gravel should be placed beneath slabs for support. This material should consist of minus '/o-inch aggregate with less than 50o/o passing the No. 4 sieve and less than l2o/o passing the No. 200 sieve. All fillmaterials for support of floor slabs should be compacted to at least95Yo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils or a suitable imported sandy gravel devoid of vegetation, topsoil and oversized rock. Underdrain System: A perimeter underdrain should not be needed for the proposed slab-on- grade construction. We recommend below-grade construction, such as retaining walls, crawlspace and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. If needed, the drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed ateach level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum lYo to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2o/opassingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least I Yz feet deep. An impervious membrane such as 20 mil PVC should be placed in a trough shape below the drain and attached to the wall with mastic to prevent wetting of the bearing soils. Kumar & Associates, lnc. @ Project No, 21-7-392 -4- Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the shop/residence has been completed: 1) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfrll should be adjusted to near optimum moisture and compacted to at least 95%o of the maximum standard Proctor density in pavement and slab areas and to at least 90Yo of the maximum standard Proctor density in landscape areas. Free-draining wall backfill (if any) should be capped with about 2 feet of the on- site, finer graded soils to reduce surface water infiltration. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 6 inches in the hrst 10 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in pavement and walkway areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the building caused by irrigation. Septic Area: Two profile pits were dug at the locations shown on Figure l. The soils exposed in the Profìle Pits shown on Figure 2 consist of I foot of topsoil overlying 3/z feet of loam over 4Yz feet of silt loam down to the bottom of the pits at 9 feet. Both soils are considered soil Type 2A per Colorado Department of Public Health Guidelines. Based on the subsurface conditions encountered, the area of Profile Pits I and 2 should be suitable for a conventional infiltration septic disposal system. A civil engineer should design the infiltration septic disposal system. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this arca at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in Kumar & Associates, lnc.0 Project No. 21-7.392 -5- this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. if conditions encountered during construction appear different from those described in this report, we should be notified at Õnce so re-evaluation of the recommendations may be made. This reporl has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design ehanges may require additional analysis or modifications to the recommendations presented herein. 'We recommend on-site observation of excavations and foundation bearing strata and testing of structural filIby a representative of the geotechnical engineer. If you have any questions or if we may be of fi,xther assistance, please let us know Respectfuliy Submitted, Kumar & Associateso I Daniel E. Rev. By: SLP DEH/kac attactunents Figure 1 - Location of Exploratory Pits Figure 2 - Logs of Expioratory Pits Figures 3 and 4- Swell-Consolidation Test Results Figures 5 and 6 - USDA Gradation Test Results Table I - Sunrmary of Laboratory Test Results t'fia(7¡ Kumar & Associates, lnc. el Project No. ?1-7-3S? J 1 U APPROXIMATE SCALE_FEET 21 -7 -392 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1 € Pll1 PIT 2 PP- 1 PP-2 0 0 WC=7.8 DD=101 WC=11.1 DD= 1 00t- L¡J r¡J LL ITt-(L tJo 5 WC 1.0 Â GRAVEL= 1I SAND=J9 Sl LT= 55 CLAY=5 GRAVEL=0I s¡ND=Jo SILT=47 CLAY=23 5 Ft¡J l¡Ju- I-t-(L IJo DD=8 WC= 1 0.5 DD=87 10 10 LEGEND TOPSOIL: SANDY SILT AND CLAY, ORGANIC, SOFT, DARK BROWN, ROOTS. CLAY (cL): SANDY, SILTY, STIFF, SLIGHTLY MOIST, BROWN SILT (ML): SANDY, STIFF, SLIGHTLY MOIST, WHITISH, CALCAREOUS. t I t HAND DRIVEN LINER SAMPLE DISTURBED BULK SAMPLE NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON APRIL 30, 2021 2. THE LOCATIONS OF ÏHE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY PITS ARE PLOTTED TO DEPTH. 4. THE EXPLORAÎORY PIT LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSTTY (pcr) (nSrV Ð 2216); GRAVEL = PERCENT RETAINED ON NO. 1 0 SIEVE; SAND = PERCENT PASSING N0.10 SIEVE AND RETAINED ON N0.325 SIEVE; SILT = PERCENT PASSING NO. 325 SIEVE TO PARTICLE SIZE .002MM; CLAY = PERCENT SMALLER THAN PARTICLE SIZE .002MM. 21 -7 -392 Kumar & Associates LOGS OF EXPLORATORY PITS Fig, 2 f SAMPLE OF: Sondy Silty Cloy FROM:Pit1@2.5' WC = 7.8 %, DD = 101 pcf NO MOVEMENT UPON WETÏING àq JJIJ =U1 I zo t- ô)o u')zo(J 0 -1 -2 -3 -4 -5 't.0 APPLIED PRESSURE - KSF 100 àq JJ UJ =U) I zo F- ôfo U1zoO 0 -1 -2 -5 -4 f.0 APPLIEO PRESSURE - KSF 10 Sondy Silt @ 6.5' %, DD = 87 pcf SAMPLE OF WC = 10.5 FROM: Pit 1 These test results opply only to the somplcs t.st.d. lh. t.stiñg r.pod sholl ¡ot be reproducad, €xcept in full, without thc writlên opprovôl ôf Kumor dnd ksociotes, lnc. Swell Consolidotioñ tcstìng p.dormcd ¡¡ occordonce with ASIM 0-4546. ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 21 -7 -392 Kumar & Associates SWELL-CONSOLIDATION TTST RESULTS Fig. 3 t I E SAMPLE OF: Sondy Silty Cloy FROM:Pil 2@2.5' WC = I 1.1 %, DD = 100 pcf ADDIÏIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING i: 1làq JJ L¡J =(n I z.otr o =o(n z,oO 1 0 -1 -2 -3 -4 -5 1.0 APPLIED PRESSURE - KSF 10 100 àq JJt! =(n I zoË ô =otnz.oo 1 0 -1 -2 -3 1.0 APPLIED PRESSURE - KSF t0 100 SAMPLE OF: Sondy Silt FROM:Pit2E^5' WC = 11.0 %, DD = 86 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE ÏO WETTING 21 -7 -392 Kumar & Associates SWELL_CONSOLIDATION TTST RESULTS Fig. 4 CU-UmzzoCN*=oaq(,1aqooo!PERCENT RETAINEDoo!oooobbb¿¡!ÞsolJ!UFm-lmnoT-o:D-to-mo)2-=m-tm1u')oIooÇ)amf-\oo\U)zUOJ(orOo\ct)t---t(¡N)\oo\ot@\oCocla)a--l-ulna.f-f.1.l1o=-u-uoC¡CNi¡IUÐm--1mÐzaØ(t(nmmzaa)Ø\\,:i.l,],"*¡ ' ' '.,t'i' ....i..t....---., .. ,.. ,.:,:llzoo!aitrzlzEscçtoPERCENT PASSINGNoN)I--lIo.r(oN)^c3o¡aeoØ(t,oo.f¡¡oØCU)g6)nO-Joz.-{rnU)-{ÐrÌl(./)ct--lU)-jIul € HYDROIVETER ANALYSIS SIEVE ANALYSIS 24 HR. 7 HR l MIN, #325 U.S, STANDARD #140 #60 #35 3t8', 3t4', 1 1t2', 3', 5',6', 8" 100 10 90 20 80 30 70 ô LJz F- L¡J É. t-z l¡JOÉ. lJJ CL 40 60 oz UI(n fL F-z t¡JoÉ L¡J Ã_ 50 40 70 30 80 20 90 10 100 0.001 .002 .005 .009 ,019 .045 .106 .025 .500 1.00 2,00 4.75 DIAMETER OF PARTICLES IN IVILLIMETERS 9.5 19.0 37.5 76.2 152 203 CLAY I I saNp I oRAVTL II v FrNr | flNr I [,lrDruN,1 |coABSr lv coAcsrl SMALL | [.4rDtu[.4 | LARGT I COBBLES GRAVEL O %SAND 3O "/"stLT 47 %CLAY 23 % USDA SOIL TYPE: Loam FROM: PP-2 @ 3.5' - 4' 21 -7 -392 Kumar & Associates USDA GRADATION TEST RESULTS Fig.6 K+rflfumar & Associates, lnc. cGeotechnical and Malerials Engineersand Environmental ScientistsTABLE 1SUMMARY OF LABORATORY TEST RESULTSProNo.21-7-392SOIL TYPE(%)CLAY(%)(%)llùGRAVELSandy Silty ClaySandy SiltUSDA SOIL TEXIURESILTSANDSandy Silty ClaySandy SiltSilt Loam (Type 2A)Loam (Type 2A)5235547393010SILT&CLAY(%)t0lSAND(%)GRADATION("/"1GRAVELNATURALDRYDENSITY(pc08710086NATURALMOISTURECONTENT("/ù7.810.slt.tI 1.0DEPTH(ft)2y,6%at/L/255-5%3%-4SAMPLE LOCATIONPITI2ProfilePit 1ProfilePit2